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THE VOYAGE OF H.M.S. CHALLENGER. 



I. Subfamily 



Tripospyrida. 

 Three basal feet. (One 

 odd caudal and two 

 paired pectoral.) 



Synopsis of the Genera of Zygospyrida. 

 Apex of the shell with one horn, 

 Apex of the shell with three horns, . 

 Apex of the shell without horns, 

 Apex with two large coryphal holes, right and left, . 



II. Subfamily 



Dipospyrida. 

 Two basal lateral feet. 

 (Originally the two 

 pectoral feet.) 



III. Subfamily 



Tetraspyrida. 

 Two sagittal and two 

 lateral feet. 



Two feet grown together and [ Feet BUnple ' 

 uniting to form a ring. \ -& , 

 Apex with a horn. 



Feet simple, not branched. 



gerieg Q 



( Apex with one horn, 

 ( Apex without a horn, 

 Apex with one horn, 

 Apex with three horns, 

 [ Apex without a horn, 



f Apex with one horn, 

 V. Subfamily | Q dal pectoral and I 



Pentaspyrida. V , , ', { i Apex with three horns, 



Five basal feet. 



[ Apex without a horn, 



IV. Subfamily 



Hexaspyrida. 

 Six basal feet. 



Apex with one horn, ..... 

 Apex with three horns (one apical and two frontal), . 



VI. Subfamily 



Therospyrida. 

 Four paired lateral < 



feet. (Two pectoral | Apex with two lateral or frontal horns, 

 and two tergal.) 



Apex without a horn, 



VII. Subfamily 



Polyspyrida. 

 Numerous (seven to 



twelve or more) 



basal feet. 



' Apex with one horn, .... 



Apex with three horns (one apical and two frontal), . 

 Apex with numerous horns, . 

 Apex without a horn, .... 



VIII. Subfamily ( Apex with one horn, . 



Circospyrida. '. 

 No basal feet. ( Apex without a horn, 



441. Tripospyris. 



442. Triceraspyris. 



443. Tristylospyris. 



444. CepTialospyris. 



445. Dipospyris. 



446. Brachiospyris. 



447. Dendrospyris. 



448. Dorcadospyris. 



449. Gamospyris 



450. Stephanospyris. 



451. Tetraspyris. 



452. Tessarospyri*. 



453. Hexaspyris. 



454. Liriospyris. 



455. Cantharospyris. 



456. Clathrospyris. 



457. jEgospyris. 



458. Pentaspyrig. 



459. Zygospyris. 



460. Elaphospyris. 



461. Taurospyris. 



462. Thei-ospyris. 



463. Petalospyris. 



464. Anthospyris. 



465. Ceratospyris. 



466. Gorgospyris. 



467. Circospyris. 



468. Dictyospyris. 



